Abstract 17540: Functional Mitral Regurgitation is Associated With Decreased Papillary Muscle Viability Patients With Non-Ischemic Dilated Cardiomyopathy

Abstract

Background: The underlying mechanisms of functional mitral regurgitation (FMR) in non-ischemic cardiomyopathy (NICM) are incompletely understood. Aims: We investigated the correlation between papillary muscle viability and FMR in NICM. Methods: We enrolled 66 patients with NICM (LVEF<40%, NHYA III) undergoing CD34 + cell transplantation. At baseline, patients underwent electroanatomical mapping; papillary muscle viability was quantified by local unipolar voltage (UV) measurement, and decreased viability was defined as UV<8.3 mV. All patients received granulocyte-colony stimulating factor; CD34 + cells were collected by apheresis and delivered by transendocardial injections. Echocardiography was performed at baseline and 6 months after cell therapy; severity of FMR was graded by multi-parametric approach. FMR improvement was defined as a reduction in FMR by ≥1 grade when compared to baseline. Results: At baseline, papillary muscle viability was decreased in 24 (36%) and preserved in 42 (64%) of patients. Moderate to severe (2-3+) FMR was more common in patients with decreased papillary muscle viability (6/24; 25%) than in patients with preserved viability (2/42; 5%, P=0.015). Transendocardial cell injections were performed in the papillary muscle area in 26 patients (Group A) and in other areas of the left ventricle in 40 patients (Group B). The groups did not differ in age (56±11 years in Group A vs. 54±10 years in Group B, P=0.32), sex (male: 96% vs. 85%, P=0.21), creatinine (0.98±0.27 mg/dL vs. 0.96±0.28 mg/dL, P=0.92), bilirubin (0.89±0.37 mg/dL vs. 0.92±0.35 mg/dL, P=0.45), LVEF (34±9% vs. 31±7%, P=0.12), NT-proBNP levels (1196±994 pg/mL vs. 1077±1176 pg/mL, P=0.68), the degree of FMR (1.28±0.78 vs. 1.02±0.38, P=0.20), or papillary muscle viability (9.9±3.0 mV vs. 10.3±3.2 mV, P=0.62). At 6 months after cell injection, FMR improved in 77% of patients in Group A vs. 13% in Group B (P=0.001). On multivariate analysis, cell injection in the papillary muscle area was an independent correlate of FMR improvement (P=0.01). Conclusions: FMR in patients with NICM is associated with decreased papillary muscle viability. Transendocardial injection of CD34 + cells in the papillary muscle area may improve FMR in this patient population.